Increasing demands for high throughput and precision performance of machine tools dictate increasingly stringent requirements on machining tolerances and part-processing times. Such requirements in turn require a high machine tool positioning bandwidth, and command-following accuracy. In meeting such stringent performance requirements, and given a broad spectrum of disturbances in the machining environment, it becomes important to identify the source of the disturbances and effectively handle propagation of such disturbances from the source to the tool output.
A major source of disturbances in machine tools is low-frequency vibrations of base platforms on which the machine tools are mounted. Such vibrations occur typically in the 1-1.0 Hz range. The vibrations result from an inherent flexibility of the base. A challenging aspect of such vibrations is that they are lightly damped, resulting in long-tailed transients and settling times, which are detrimental to tracking performance in the machine tools.
Many advanced command generation techniques, such as input shaping, and control techniques involving feedforward and feedback, are known for minimizing residual vibrations.
It is desired to attenuation of residual vibrations not only in the tool or load output, but also the source, i.e., the base platform supporting the machine tool. Attenuating vibrations of the base platform is critical to minimizing cross-talk and propagation of disturbance between machine tools supported on the same base platform. For these dual requirements of achieving acceptable tracking performance, i.e., high bandwidths or low settling times, as well as the attenuation of base vibrations, a single linear controller is limited by inherent performance tradeoffs.